It's difficult to tell from this shot but I'd say the map's in colour (albeit very 'knocked back'). Assuming the wall maps were the same as the public handout (and I belive they were), and looking at MILL HILL EAST which is shown below the line (blurred but if you have a selection of maps it's easily discernable, then this would make it Undergorund Map 1941 Issue 2. 1941 Issue 1 was sepia and white with MILL HILL EAST above the line.
1940 Issues 1 and 2 were both black/sepia and white with MILL HILL EAST above the line.